JPS60897B2 - injection molding system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to an improved edge-gated injection molding system.

In a typical edge-gated system, several mold cavities are placed in a cooled mold plate around a central heated nozzle or bushing.

The temperature and heat flow characteristics of the gate area are of great importance since there are no valves or other insulating means to assist in controlling the flow rate of the melt. The system is capable of rapidly and repeatedly filling a mold cavity and then opening it to release the molded product without clogging and without excessive sagging. Must be able to do it. For this purpose, insulation or partial insulation is provided between the heated bushing and the cooled mold plate so that the bushing is kept at a high enough temperature to keep the melt in a molten state and the mold plate is heated. , it is necessary to ensure that when the melt flows into the mold cavity it remains cool enough to solidify quickly. Traditionally, this insulation has been accomplished by forming a space between the pusher and the mold plate adjacent the valve gate and filling this space with melt.

The melt solidifies at least adjacent the cold mold plate, thereby providing some degree of insulation between the bushing and the mold plate. For example, the present inventor's U.S. Pat.
No. 447, "Heater Castings for Multi-Mold Hole Hot Runner Edge Gates," both disclose systems having such means and in which the radial portion of the runner passage is in direct contact with the mold plate. There is. However, these nozzle seals with valve gates have also traditionally been used in injection molding systems.
This system is covered by U.S. Patent No. 4,043,740, "Injection Molded Nozzle Seal," issued August 23, 1977, and Canadian Patent Application No. 356,233, filed July 15, 1977.
No. ``Injection Molding Nozzle Seals''. In both of these applications, the nozzle seal acts to transfer additional heat to the area of the gate, which facilitates the seating of the valve, improves the reliability of the system, and improves the actuation of the valve pin actuation mechanism. Extends lifespan. In fact, in the aforementioned Canadian Patent Application No. 356,233, the nozzle seal itself actually forms the gate itself upon which the valve pin tip sits. The fact that these advantages are only available for gated systems reduces the likelihood that such seals will be installed in pond-type molding systems.

In particular, in green-gated molding systems, these seals tend not to be used in twill-gated systems because the mold plate walls containing the gates are curved. The reason is that the problem of leakage of the pressurized melt exists in this case. If melt leaks in the gate area, this melt will flow into the air gap between the bushing and the mold plate and cause the aforementioned problems.It is therefore an object of the invention to The object of the present invention is to provide a green-gated injection molding system that operates using seals to at least partially eliminate the aforementioned drawbacks.

To this end, in one feature, the invention includes cooled mold plate means forming at least one openable mold cavity; an electrically heated sprue bushing, said wellbore having an inner wall spaced from the sprue bushing to form an insulating air gap, and said sprue bushing having an elongated central melt passageway, said central passageway having a melt inlet. at least one groove extending radially outwardly from said central passage to at least one corresponding green gate in the mold plate means, the green gate extending into said mold cavity;
including at least one corresponding hollow seal having a central aperture extending between an inner end and an outer end, said seal being dome-shaped with a central entrance, said seal extending across said air gap, a central hole is aligned with the radially extending groove and the gate, the inner end is seated within a recess in a sprue push, and the outer end abuts an inner wall of a vertical hole in the mold plate. , at least a portion of said wall slopes slightly inwardly so that the seal gradually deforms slightly inwardly as the sprue bushing is inserted into the well, and the system is pressurized. The present invention provides a hot runner edge gated injection molding system that includes: heating to operating temperatures to prevent substantial leakage of melt into the air gap;

Other objects and advantages of the invention will become apparent from the following description based on the figures.

Referring to the figures, the green-gated injection molding system has at least one hollow sprue pusher 10 with a central hot runner passageway 12 extending therethrough.

The passageway 12 extends from the manifold plate 14 and branches into a number of grooves 16 which extend radially outwardly from the central passageway 12. Each groove 16 extends outwardly from the hollow seal 1.
8 to a gate 20 leading to a mold hole 22. The sprue bushing is electrically heated and is claimed in Canadian Patent Application No. 317 filed in Canada on December 14, 1979 by the present inventor.
No. 948 “Gate bushing with cast-in heating element” and 1
It can be of the type shown in "Gate Bushing and Manufacturing Method" filed in Canada on October 24th by King No. 98.

It has a corrosion-resistant inner section 24 forming the central passage 12, a spiral heating element 26 surrounding the inner section 24, and a highly conductive section 28 cast over these. In the preferred embodiment, the inner portion 24 is made of a beryllium nickel alloy that resists the corrosive effects of the melt, and the conductive portion is made of a beryllium steel alloy that conducts heat rapidly and evenly from the heating element 26 to the inner portions 2-4. The sprue bushing 10 is located in the vertical hole 30 in the mold hole plate 32.
It is seated inside and firmly held in the normal position by an insulating bushing 34. When sprue bushing 10 is heated by heating element 26 and mold plate 32 is cooled by cooling element 36, insulating bushing 34 maintains an air gap 38 between them to reduce heat loss. As shown in FIG. 2, the valley hollow seal 18 extends from a central bore 40' to an extension 42 to a central aperture 44 in a domed outer end 46. As shown in FIG.

Valley hollow seal 18 extends across air gap 38 and extends its inner end 42 into one radial groove 16 in sprue bushing 10.
is seated in the recess 48 around the mold plate 3, and its outer end is placed in the mold hole plate 3.
It is made to abut against the inner wall 50 of the vertical hole 30 in 2. As shown,
The domed outer end 46 has a substantially planar sealing surface 52;
This surface is formed by pressing and deforming the mold cavity plate 32 around the gate 20 leading to one mold cavity 22. In this position, the entrance in the domed outer end 46 of the seal 18 is aligned with the gate 20 and the central hole 40 communicates with one radial groove 16. Hollow seal 18 is made of metal to provide sufficient strength to withstand repeated high-pressure loads, but this metal does not allow excessive heat to escape from sprue pusher 10 to mold cavity 32.
It should not be made of a highly conductive metal to prevent it from being transmitted to the metal. In a preferred embodiment, hollow seal 18 is made of titanium alloy or stainless steel. In use: During assembly of this system, the seal 18 is placed in each recess 48 and the sprue bushing 10 is then pressed into the well 30 until it seats on the insulating bushing 34.

The size of the sprue pusher 10 and the seal 18 is such that their effective combined radius is the inner wall 50 of the vertical hole 30 at the location of the gate 20.
The radius shall be approximately 0.005 inch (approximately 0.127 side) larger than the radius of . Therefore, to facilitate insertion of the L sprue bushing 10, the portion 54 of the wall 50 is sloped slightly inwardly into the gate 20. Thus, when the sprue bushing 10 is pressed into the well 30, the domed outer end 46 of the seal 18 contacts the sloped portion 54 of the wall 50 and, when placed in position around the gate 20, is slightly elastic. deforms inward. During insertion, the outer surface of the insulating pusher 34 is received within the cylindrical portion of the wall 50 of the well 30 of the mold plate and is aligned to properly align the sprue bushing 10.
This allows the sprue bushing to deform and align properly to form a secure seal. When the sprue bushing 10 is heated to operating temperature, it expands and the domed contour 46 of the seal 18 undergoes further deformation. Due to the shape of the seal 18 causing this slight inward deformation, a pressure-tight seal is formed against the curved inner wall 50 of the vertical hole 30. This same problem could be solved by grinding the end of each seal 18 into a curved inner wall 50, but this technique is expensive to implement and the seal 18 is always inserted in the correct orientation. The downside is that you have to. If leakage occurs between the seal 18 and the curved wall 50 by repeatedly applying high injection pressures to the heated melt, the melt will escape into the air gap 38, thereby reducing the insulation effect and reducing the color. Problems as described above arise when changing materials. After assembly, sprue bushing 10 is heated by applying power to heating element 26 via lead wire 56.

A thermocouple (not shown) is usually included to precisely control the temperature. After the mold plate 32 is cooled by cooling elements 36 and the temperature has stabilized to operating conditions, the hot pressurized melt is delivered from a molding machine (not shown) or other source. The melt flows from manifold plate 14 through central passage 12, branches into radially extending grooves 16, passes through seal 18,
Enter mold hole 22. After the mold cavity is filled, the injection pressure is removed from the melt, and after the melt in the cooled mold cavity has solidified, the mold is opened and the molded product is released. The mold is then closed and the process repeated. This process is important in that it can be repeated reliably without leakage into the air gap. This is true for engineering flame retardant materials that are difficult to mold, such as polycarbonate, polyphenylene sulfide, polyphenylene oxide, and nylon 66. This is because these materials deteriorate in quality if they fall into the air gap 38. In systems where the heating element 26 extends down close to the gate 20, the heat is applied close to the air gap 38 and the degradation of the melt quality increases to an unacceptable level. It turns out. Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and those skilled in the art can make various design changes.

For example, although a multi-hole system has been described, it is clear that the present invention also includes a single-hole system. Additionally, the shape of the outer end of the seal that deforms to form a pressure seal against the curved inner wall of the mold plate may be modified.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a portion of a preferred edge-gated injection molding system of the present invention, and FIG. 2 is an enlarged cross-sectional view showing the relationship between one seal and a corresponding gate in a mold plate. 10...Hollow sprue bush, 12...Medium D
Hot runner passage, 14... Manifold plate,
16...Miso, 18...Hollow seal,
20...Gate, 24...Inner part, 26...
... Heating element, 28 ... Highly conductive part, 30
...Vertical hole, 32...Mold hole plate, 34...
...Insulation bushing, 36...Cooling element, 38
...'Air gap, 40... Center 21, 4
6...Dome-shaped outer end, 48...Concavity, 50...
·…inner wall. FIG. 1. FIG. 2.

Claims (1)

[Scope of Claims] 1. In an injection molding system with a hot runner edge gate, the configurations (a) to (c), that is, (a) at least one
(b) a hollow electrically heated sprue bushing securely seated within a well in the mold hole plate means, the wells forming two releasable mold holes; having an inner wall spaced from the sprue bushing to form an insulating air gap, the sprue bushing having an elongated central melt passage extending from the melt inlet to at least one groove, the slot extending from the central passageway; extending radially outwardly to at least one corresponding edge gate in the mold hole plate means, the edge gate extending into said mold cavity; (c) at least a central hole extending between an inner end and an outer end; one corresponding hollow seal, said seal having a dome shape with a central opening, said seal extending across said air gap and aligning said central hole with said radially extending groove and said gate; said inner end seats within a recess in a sprue bushing, said outer end abuts an inner wall of a vertical hole in a mold plate, and at least a portion of said wall slopes slightly inwardly. , so that the seal gradually deforms slightly inwardly when the sprue bushing is inserted into the well, and the system prevents substantial leakage of pressurized melt into the air gap. What is claimed is: 1. A hot runner edge gated injection molding system comprising: being heated to a working temperature to prevent 2. In the hot runner edge gated injection molding system of claim 1, a plurality of grooves extend radially outwardly from the central passageway to a corresponding seal, each aligned with a corresponding gate in a corresponding mold cavity. A system characterized by: 3. In the injection molding system with a hot runner edge gate according to claim 1, the inner wall of the vertical hole in the mold hole plate is
A system comprising an alignment portion for receiving alignment means carried on the sprue bushing when the sprue bushing is inserted into the well to ensure proper alignment of the sprue bushing when deformation of the seal occurs. 4. An injection molding system with a hot runner edge gate according to any one of claims 1 to 3, characterized in that the seal is made of a titanium alloy.